Comtrol eCos - Manual (Page 514)

Chapter 38. TCP/IP Library Reference
only IPv4 and not IPv6, then the ai_family member of the hints structure
should be set to PF_INET when getaddrinfo() is called. If the third
argument to getaddrinfo() is a null pointer, this is the same as if the
caller had filled in an addrinfo structure initialized to zero with
ai_family set to PF_UNSPEC.
Upon successful return a pointer to a linked list of one or more addrinfo
structures is returned through the final argument. The caller can pro-
cess each addrinfo structure in this list by following the ai_next
pointer, until a null pointer is encountered. In each returned addrinfo
structure the three members ai_family, ai_socktype, and ai_protocol are
the corresponding arguments for a call to the socket() function. In each
addrinfo structure the ai_addr member points to a filled-in socket
address structure whose length is specified by the ai_addrlen member.
If the AI_PASSIVE bit is set in the ai_flags member of the hints struc-
ture, then the caller plans to use the returned socket address structure
in a call to bind(). In this case, if the nodename argument is a null
pointer, then the IP address portion of the socket address structure will
be set to INADDR_ANY for an IPv4 address or IN6ADDR_ANY_INIT for an IPv6
address.
If the AI_PASSIVE bit is not set in the ai_flags member of the hints
structure, then the returned socket address structure will be ready for a
call to connect() (for a connection-oriented protocol) or either
connect(), sendto(), or sendmsg() (for a connectionless protocol). In
this case, if the nodename argument is a null pointer, then the IP
address portion of the socket address structure will be set to the loop-
back address.
If the AI_CANONNAME bit is set in the ai_flags member of the hints struc-
ture, then upon successful return the ai_canonname member of the first
addrinfo structure in the linked list will point to a NUL-terminated
string containing the canonical name of the specified nodename.
If the AI_NUMERICHOST bit is set in the ai_flags member of the hints
structure, then a non-null nodename string must be a numeric host address
string. Otherwise an error of EAI_NONAME is returned. This flag pre-
vents any type of name resolution service (e.g., the DNS) from being
called.
The arguments to getaddrinfo() must sufficiently be consistent and unam-
biguous. Here are pitfall cases you may encounter:
o getaddrinfo() will raise an error if members of the hints structure
are not consistent. For example, for internet address families,
getaddrinfo() will raise an error if you specify SOCK_STREAM to
ai_socktype while you specify IPPROTO_UDP to ai_protocol.
o If you specify a servname which is defined only for certain
ai_socktype, getaddrinfo() will raise an error because the arguments
are not consistent. For example, getaddrinfo() will raise an error
if you ask for “tftp” service on SOCK_STREAM.
o For internet address families, if you specify servname while you set
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